1. Field of Invention
This invention relates to off-the-road large pneumatic tires, such as are commonly used on earthmoving equipment, and more particularly to large pneumatic tires having a specified clearance relationship between the lower bead area of the tire and a flange portion of an associated rim upon which the tire is designed to be mounted.
2. Description of the Related Art
Large pneumatic tires to be used on earthmoving equipment, commonly known as earthmover tires, are well-known. Earthmover tires are required to perform in difficult environments. When used "off-the-road", they are required to provide excellent traction for extremely heavy vehicles pushing, pulling and lifting extremely heavy loads. The environment is also fraught with rocks and other sharp instruments which can damage the tires. Due to the relatively high cost of these large tires, durability and long life is a primary design parameter.
A second environment in which the tires might be expected to form is that of public highways. Sometimes the earthmoving equipment must travel on public highways as the vehicles travel from construction site to construction site.
Previously, the required strength was built into such tires through the incorporation of certain curves into the molded shape of the exterior of the tire. These extra curves or bulges were believed to give extra support to those areas of the tire where durability was especially important, such as the lower sidewall, mid sidewall and tread center. In the bead flange area, the prior art off-the-road tires employed an interference fit whereby the tire was in contact along the radially outer surface of the rim flange. Off-the-road tire engineers conventionally add mass to structurally improve the durability of the tire.
In the aircraft tire art, tire engineers must always look to reduced mass, due to the unique weight limitations of that art's area, yet the tires must still be durable.
In U.S. Pat. Nos. 4,790,364 and 4,813,467, an aircraft tire and rim combination is disclosed which shows a clearance between a rim flange and the surface of the bead portion of the tire. However, these inventions concern aircraft tires which are much different in construction and application than earthmover tires. They are also designed to be used on aircraft rims, such as H-type rims, which are different in design than earthmover or off-the-road rims. In addition, the tires shown in U.S. Pat. Nos. 4,790,364 and 4,813,467 do not have inflection points in the ply, as does the present invention.
The present invention also has as one of its objects improved durability in the earthmover tire, but does so by providing a bead area design which has demonstrated a marked improvement over the prior art.
It is therefore an object of the invention to provide an earthmover tire having improved durability.
It is another object of the invention to provide an earthmover tire having a bead portion which cooperates with a flange portion of an associated rim to improve the durability of the tire.
It is a further object of the invention to provide an earthmover tire having a certain relationship between the bead flange area of the tire and the rim flange, such relationship creating a clearance therebetween. The nature of the clearance is discussed herein and meets certain requirements in order to provide the durability sought.